Currently, use of a small-size wireless base station called an access point base station (or a femtocell base station or a femtocell) is spreading for environmental improvement in interior wireless communication. In the interior of houses or buildings, the access point base station performs wireless communication with a plurality of mobile terminals, and is coupled to a network through a wired backhaul connection such as ADSL (Asymmetric Digital Subscriber Line). In such an access point base station, in order to avoid interference with other base stations around the access point base station, the quality of the wireless link is measured, and the transmission power is controlled according to the measurement result.
Japanese Laid-open Patent Publication No. 2002-043959 discloses a use of transmission power control in wireless communication in a communication system in which relatively massive data are transmitted through a wired section and a wireless section. In this communication system, it is recognized that the wireless section has a lower transmission rate than the wired section. Based on this recognition, data which has been transmitted through a wired section is temporarily stored by a data buffering means in an access point base station before the data is wirelessly transmitted to a destination (requesting the data). The data transfer rate in the wireless section is increased by the access point base station when the amount of data accumulated in the data buffering means is large. At this time, the increase in the data transfer rate is realized by an increase in the transmission power.
Furthermore, International Patent Publication No. WO2006/110492 discloses a mesh wireless communication network which is constituted by a plurality of mesh points (MPs). In the mesh wireless communication network, information on setting of an allowed power level is transmitted from an existing MP to a new MP, and the new MP adjusts the power level in accordance with the transmitted information.
The recent development in the wireless communication technology toward IEEE802.11n and 4G (fourth generation of cellular wireless standards) has raised expectations for further increase in the transmission rate in wireless communication. With such a high transmission rate in wireless communication, a very high transmission power is expected to be used in the wireless links between the access point base station and mobile terminals, and can therefore cause interference with other cells around the access point base station.
On the other hand, the transmission rates in the wireless links between mobile terminals and a communication device such as the access point base station are expected to exceed the transmission rate in the wired link through a backhaul line in the future. If the transmission power is adjusted when the amount of data accumulated in the data buffering means in the access point base station is determined to be large, as in the conventional communication system mentioned above, the data transfer is delayed because the data buffering means has to wait until a predetermined time elapses for measuring the amount of the accumulated data.